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Abstract

We apply generalized ellipsometry, well-known to be sensitive to the optical properties of
anisotropic materials, to determine the amount of fibronectin protein that
adsorbs onto a Ti slanted columnar thin film from solution. We find that the
anisotropic optical properties of the thin film change upon organic adsorption.
An optical model for ellipsometry data analysis incorporates an anisotropic
Bruggeman effective medium approximation. We find that differences in
experimental data from before and after fibronectin adsorption can be solely
attributable to the uptake of fibronectin within the slanted columnar thin film.
Simultaneous, in-situ generalized ellipsometry and quartz
crystal microbalance measurements show excellent agreement on the amount and
rate of fibronectin adsorption. Quantitative characterization of organic
materials within three-dimensional, optically anisotropic slanted columnar thin
films could permit their use in optical sensor applications.

Figures (6)

Effective medium scenarios with mixtures of ellipsoidal inclusions (general case) and a homogeneous host matrix. The mixture with randomly oriented inclusions (a) exhibits an average effective polarizability 〈Peff〉 whereas the mixture with aligned inclusions (b) shows anisotropic properties with three effective polarizability components Peff,j. The major polarizability axes system rendering the biaxial nature of the film is depicted in (c).

Surface density and volumetric fraction parameters during FN adsorption and PBS rinsing. FN solution is introduced at t = 147 min, and rinsing begins at t = 182 min. fads and its error bars (in many cases overlapped by data points due to small error) are taken directly from the results of the AB-EMA model.